Left IPhone 6 s plus in heat

I left my iPhone on my mower seat while I was cleaning the deck. It was only on there for about 10 minutes and it said IPhone needs to cool down before you can use it. I let it cool down and everything seems alright but I just wanted to know if that could damage the phone or am I just worrying about something stupid thanks.

Which smartphone should i buy?

Samsung galaxy J7 or iphone SE.

I have been warned not to buy iphone but I don't understand why, any idea.
if not these, what smart phone should i buy?

How much should I sell an iPhone 5s for?

I have a 16GB, space grey, iPhone 5s that I just brought about a year and a half ago. I have a new phone now and don't use it, I originally brought it for $500 and it's still in really good condition (No scratches, no cracks, no water damage, all buttons work, sound works, cameras both work and I have never actually dropped it and I never needed to get it any repairs done) so what would be a reasonable price to sell it for?

Is my coach a scammer?

I was trying to sell it off to buy the latest iphone, and my coach came up to me and told me that she wanted to buy my phone. My phone was brand new, I've used it for only a month and the price I suggested was way cheaper than the initial price. So she took the phone from me and told me she was going to pay it later in the evening. Evening came, she paid me LESS than 1/4 of the suggested price. She told me before this that she was going to pay the full price to me and now she wanted to pay it monthly after she got the phone. So I called her and told her that I want my phone back and I'm not willing to sell it to her since it was not as we bargained. And two days passed, the phone is still with her. Mind you, my phone is super brand new; i rarely use it because I have a Samsung. I'm afraid that she's going to switch it with a fake iphone or scratch it. Is there a way to check the serial number of the iphone? What should I do?